is dual exhaust harm full?

I got into a huge debate/argument about dual exhaust to dayin one of my college classes. I and another classmate were talking aboutexhaust upgrades and I said I wanted dual exhaust. A guy next to me chimed inand said just remove everything and put two pipes out the back with no muffleror anything. I began to explain that doing so would be harmful to the motorbecause the cylinders could not equal out causing major performance problems. Heand another guy got all upset saying it does not matter and if I was true thenhow do people run open headers on hot rods and such. Not having an answer tothat I gave up and quit talking. So who is right? Why do you need to put an xpipe in and how do the hot rods get away with having open headers. I have a2001 silverado 5.3L also

I can't give you an exact answer. But, someone will come along that can. I can tell you that I had duels installed on my 1995 silverado. The guy did not install a crossover like he said he was going to. I lost power, it did not sound all that good and it ran crappy (idled rough). The pipe from the passenger side was a straight shot from the header to the muffler and out the back. The driverside pipe had to have multiple bends to go around things. The passenger side pipe would pop like crazy. After a week I could no longer stand it and took it back to the shop. The guy installed a x pipe, my power increased significantly, the idle smoothed out and the popping sound disappeared. I have seen many guys run with no muffler or cats, but they usually still have the factory y pipe. As far as open headers go on hot rods, I could be wrong on this, but the pressure would be equal because there is no pipe, just headers open to the atmospheric pressure.

I dont have scientific data... but straight dual exhaust will not damage the engine also long as it is tuned correctly (fuel mixture). Running to lean or rich could damage the engine. What the x-over pipe really does is even out back pressure allowing for easier tuning. My thoughts on no mufflers are is that there is not enough back pressure to allow exhaust temps to come up which created kind of a vaccum/cyclone effect to help pull the spent gases out at a rate allowing the engine to effectively burn all the fuel. Thats not enough back would lower gas mileage... basically because allot of the fuel ends up burning in the exhaust where it not building horsepower. Now running open headers and exhaust are fine for really high displacement engines where you want to get as much air/fuel thru the engine to get as much ponies as you can. That's my 2 cents.

A lot of people will tell you that an engine needs back pressure to breath properly, IMO, that's like you trying to breath through a hose. An engine is just an air pump, remove the exhaust completely and the engine will pump air more efficiently. That is why, a drag car, or a hot rod, will have open pipes, to get rid of the flow restrictions.

However, most of us do not drive in that fashion and our trucks (and cars) need exhausts; not just for the noise reasons, we require heat to burn off the pollutants The exhaust holds engine heat and, creates some heat from the restrictions and, of course, from the cat.

Because there is more pipe, and reduced flow, a dual pipe exhaust may not be as gas friendly as a single pipe. The improved efficiency may be offset by the heat sink effect of the additional metal.

Just to talk about the back pressure thing, the old 2 stroke (mix gas and oil) engines did require some back pressure, just to slow down the air flow, so there would be more complete burn.

And the x pipe; as someone suggested, it helps balance the two halves of the engine for smother operation, it will also change the sound of the exhaust, because there will be some sound wave cancelling going on.

@newcheylover:
Some good responses, so far. Add it all up and the answer is 'no', dual exhaust is not harmful, it's just different. It has some advantages such as looks, sound, and potentially less restricted air flow (which can mean more ponies) depending on implementation ... but it can also be more polluting and cause you to burn more fuel. (More air means more fuel ... which together mean more ponies ... if implemented well!)

It's all in what you like/want, really. If fuel econ and low pollution were a deal breaker for those of us on this forum, we'd be driving eco-friendly electrics/hybrids/solars and posting on some silly green go-kart forum instead of a truck forum.

Running open headers on our trucks can cause problems but as long as you got tubing past the cab you'll be fine. My cobra and 65 have exhaust cut out right under the driver and passenger seat but they are high performance motors. I used to run them on my old dodge and it never cause an issue but I lost tons of low end grunt

It depends on several variables in the engine, on whether it will be good or bad for your engine. For a new GM Vortec 5.3, straight duals will have some impact on performance, as the firing order and cam timing, are not suited to it, and the stock components are not built to run the engine at 6000+ RPM constantly, as the engine in a drag car is.

The Corvette for example comes with dual exhaust, but does have a small cross-over H connector in the center pipe. It's a more performance oriented vehicle than a Silverado though.

Having the right exhaust design for the engine and vehicle application can contribute to improved performance, fuel economy, and sound. With straight dual exhaust, on your Silverado, you'll most likely sacrifice some MPG, and a slight loss in low RPM performance, for maybe a couple HP increase in the upper RPM range, and the deeper alternating burbling sound at idle and throughout the normal driving RPM range.

I have been running a 97 firebird with an LT1 in it with open headers for two years now, I love the sound of it and have had no driveability issues with it at all.

On the other hand, I tried to run my LS1 with open headers and the ECM freaked out and had it running so rich it would burn your eyes, and it actually dripped gas out of the collectors. Older engines don't really mind, newer one's don't like open headers.

I have been running a 97 firebird with an LT1 in it with open headers for two years now, I love the sound of it and have had no driveability issues with it at all.

On the other hand, I tried to run my LS1 with open headers and the ECM freaked out and had it running so rich it would burn your eyes, and it actually dripped gas out of the collectors. Older engines don't really mind, newer one's don't like open headers.

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You really need the cats and both forward and aft O2 sensors, with sufficient piping after the cat to avoid backdraft of open air into the system (which would make the O2 read very lean). Just putting the forward and aft O2 sensors right next to each other in the pipe would definitely cause problems as well.

Of course, you could also retune the O2 sensors out, for off-road only use.